- automatic Baudrate detection and callibration- works without callibration with 8Mhz or 16MHz sysclk ( possibly 1MHz, not testet )- very simply hardware circuit: 2 resistors and a 100nF capacitor to connect to the audio line- only one pin for data transmission needed and an additional pin for a status led- low memory footprint: 800 bytes- java program to generate the sound, works on win and linux

As line coding scheme Manchester-coding is used. With this type of coding we achieve only half the transmission speed than with "Flankenkodierung" used in Soundrxtx. Therefore the mean value of the signal is more stable and no calibration potientiometer is needed.

Edit: I found a major bug. Some sound cards have an inverted output which would not work with the bootloader. I made a second java program which corrects this issue. Please use the program version which fits to your computer. You will find it in the zip-file.Edit: There was another problem: some programs using interrupts did not run. Now the bootloader ( v1.3 ) has an improved initialisation to run the user program.

There is a new Bootloader with differential manchester coding now working on all sound cards ( inverted and not inverted outputs ). There is also a java programming file which creates wav-files with half the frequency. This wav file can be compressed to mp3 with 320kBit/s.

Thanks to Johannes for the hints and the "research" how to compress the wav-files to mp3 files.